The present invention relates to methods and compositions for the control and extermination of fossorial rodents.
Fossorial rodents include Richardson ground squirrels (Spermophilus richardsonii), commonly referred to as gophers, which are a destructive pest species throughout the prairie regions of North America. The burrowing and feeding activities of ground squirrels impact heavily on forage and grain crops. The burrows themselves create a physical hazard to horses, cattle, farm equipment and the unwary pedestrian. Other fossorial rodents such as Norway rats (Ratus norvegicus) and pocket gophers (Thomomys talpoides) are also considered pests. Norway rats in particular are difficult to control in both urban and rural settings.
Conventional methods for controlling ground squirrels include the use of poisoned bait, smoke bombs, water-flooding the burrow systems and even the physical removal of ground squirrels from their burrows using large vehicle mounted vacuum systems. Each of these prior art methods is unsatisfactory or ineffective for various reasons.
The use of strychnine and similar poisons is environmentally disadvantageous because of the danger posed to pets, predators and scavengers which may feed on the dead ground squirrels or the poisoned bait itself. These may include such valued species as hawks, eagles, owls, coyotes, badgers and the like. Because of this danger, there is Canadian legislation which limits the concentration of the poison which may be used, which limits the effectiveness of the poison. In mid-summer when food supplies for rodents are abundant, the effectiveness of baited poisons in dilute concentrations approaches nil.
Flooding burrow systems with water is rarely effective because the water never completely floods out the burrow; there are always anticlinal air pockets in the burrow system which allow the ground squirrels to survive until the water is absorbed into the ground. The vacuum systems are elaborate, labour intensive and expensive to operate.
Foam-based rodent control systems are known. In most cases, the foam is used as a carrier for a poison which is ingested by the rodent. In U.S. Pat. No. 3,816,610 issued to Lusby, a rigid or flexible foam plastic is used to carry a rodenticide. The foam is applied to block openings to a burrow or a hole in which the target rodent resides. It is intended that the rodent eat the foam to reopen the blocked opening and thereby ingest the poison.
Adhesive foams containing rodenticide have been used which stick to the rodent causing grooming behaviour. This causes the rodenticide to be taken up orally.
In U.S. Pat. No. 3,473,252 issued to Kramer et al., a method of exterminating rats using foams comprising hardenable synthetic resins is disclosed. These foams are propelled into holes to envelop the rat and asphyxiate the rat by displacing air present in the hole. The foam then hardens into a permanent plastic which entombs the rat remains. The preferred foam disclosed is based on a urea formaldehyde synthetic resin which polymerizes to form the permanent foam. Urea formaldehyde foams are no longer used due to their potential harmful effects on humans. The other foams disclosed may not be economically used in this manner. The permanent nature of these foams have adverse effects on the environment when used in applications not involving building structures. As well, the dead animal remains cannot be buried or otherwise disposed of because of the permanent nature of the foam.
Therefore, there is a need in the art for a control system for ground squirrels and other rodents which mitigates the disadvantages of the prior art. In particular, there is a need for a control system which is humane, effective, non-toxic to livestock, predators, scavengers and pets and is environmentally friendly.
In one aspect of the invention, the invention comprises a method of exterminating burrowing animals, said method comprising the steps of passing a treatment composition comprising a foaming agent through an aerating nozzle down a burrow containing an animal such that the burrow is substantially filled with a non-persistent foam, thereby forcing the animal to inhale the foam. In the preferred embodiment, the treatment composition used in the method is biodegradable and further comprises a respiratory irritant. It has been found that the respiratory irritant is preferably finely ground seeds of plants of the genus Brassica (family Cruciferae), commonly referred to mustard. In particular, ordinary mustard, also known as white or yellow mustard, is used. These seeds are from Brassica alba (also known as Brassica hirta or Sinapis alba) or white mustard.
In another aspect of the invention, the invention comprises a composition for use in the extermination of a burrowing animal resident in a burrow, said composition comprising a foaming agent and a respiratory irritant. In the preferred embodiment, the respiratory irritant is ground mustard seed.
In another aspect of the invention, the invention comprises the use of a composition for asphyxiating a burrowing animal resident in a burrow, wherein said composition comprises a foaming agent and does not include a synthetic resin. In yet another aspect, the invention comprises the use of a non-persistent foam composition for asphyxiating a burrowing animal resident in a burrow.
The concentration of finely ground mustard in preferred embodiments of the invention is between about 0.3% and about 0.5% (w:v) when diluted and ready to use. The invention may be supplied in a concentrated form which is diluted with water to use level concentrations.
The foaming agent may be a liquid surfactant which forms a relatively stable and dense non-persistent foam when aerated. In the preferred embodiment, the foaming agent is a commercially available aqueous forest fire suppressant foam which is biodegradable.